The woman found dead along a Kentucky highway in 1968, wrapped in a circus tent, went unclaimed for decades and was buried in a potter’s field with a gravestone that called her, simply, “Tent Girl.” Thirty years later, her identity was uncovered with the help of technology that didn’t exist when she died: mitochondrial DNA testing and, perhaps more importantly, the Internet.

Thanks to a legion of armchair detectives who scour online listings of the unidentified dead for clues to who they are, Tent Girl and others have been buried properly — and their families have been given closure, and occasionally their killers brought to justice — years or decades after their cases went cold.

In “The Skeleton Crew,’’ journalist Deborah Halber aims her magnifying glass at these amateur detectives, the would-be Marples and Holmeses of our day. Armed with little more than intuition and an Internet connection, they solve puzzles that the police sometimes cannot, matching the telltale features of unclaimed corpses with details from missing-persons reports.

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Halber’s study of the hidden world of cybersleuths is captivating, partly because she so clearly relishes her subject and reveres her sources. At times, she blurs the line to become one of them herself. Narrating her own efforts to identify a young woman found in the Provincetown dunes in 1974 with her hands severed, Halber speculates that Boston mobster Whitey Bulger might have been involved. Since the woman’s hands were never found, there were no fingerprints to help identify her.

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Even Halber’s voice is inflected with the gritty timbre of a noir detective; it’s hard not to imagine her spitting the words out of the side of her mouth. While visiting a coroner in Clark County, Nevada, she remarks, “It was only seven in the morning but I was wearing the desert heat like a lead suit.” She later attends a luncheon in a ballroom with floor-to-ceiling drapes and oversized tassels she describes, using an image from the Provincetown case, as “the size of dismembered hands.”

When she hits her stride, Halber writes vividly and engagingly about long-ago crimes and the modern-day detectives who breathe new life into closed cases. The book is thoroughly researched and abundantly detailed, although at times so much so as to overburden the reader with threads that become tangled in the telling. The narrative sometimes jumps track unexpectedly, suddenly switching focus from sleuth to victim or lurching abruptly in time or place.

Structured as a series of vignettes about some of the major players in the world of Web sleuthing, the book documents the online advances that have made their big solves possible, such as databases of coroners’ photos and sophisticated reconstructions of decomposed faces. More than how they do what they do, though, Halber wants to know why — what gets them hooked on work that is often gory, seldom paid, and rarely recognized, especially since they often meet with resistance or even antagonism from police when they share their findings.

Some sleuths are factory workers or grocery store employees for whom investigating cold cases is a way to escape the drudgery of their day jobs. For others, it’s a competition, and each case solved is a macabre trophy to their deductive abilities. The common denominator, however, is loss: Nearly everyone Halber profiles was drawn into this world after losing a loved one of his or her own and enduring the agonizing wait for closure.

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One of Halber’s most penetrating insights is that naming the unnamed seems to provide a doubled sense of identity. Many who do this work are misfits in their own right who struggle with real-world relationships and are more at ease in online groups, known only by screen names. That they take immense pleasure in giving an identity to the unidentified speaks to their own search for identity and belonging. With Halber they have found a loving home, where they are portrayed as larger than life characters and lauded as heroes.

Jennifer Latson is writing a narrative nonfiction book about a genetic disorder called Williams syndrome, which makes people socially uninhibited and indiscrimi-nately friendly.
Follow her on Twitter @JennieLatson.